This proposal is to follow 9,039 girls and 7,843 boys, currently ages 14- 19., through their transition to late adolescence and early adulthood. The girls and boys are members of the Growing Up Today Study, which was established in 1996 when the participants were 9 to 14 years of age. The cohort was initially funded by NIDDK to assess predictors of dietary intake, activity, and weight gain during a four year period. We now seek to follow the cohort for five additional years to investigate determinants of purging (i.e., use of vomiting or laxatives) and eating disorders of at least sub-syndromal severity. The mothers of the children are participants in the ongoing Nurses' Health Study II and have been followed biennially since 1989. We will obtain information annually from the participants, as well as continue to collect information from the mothers on their weight, concern with weight, weight control behaviors, and concern with their child's weight. Using this data we will assess the predictiveness of personal factors, peer influences, family influences and media influences on the development and course of purging and eating disorders of at least subsyndromal severity. Eating disorders are difficult to treat, Therefore, we believe it is essential to identify and quantify their risk factors so that better means of prevention can be developed. Not only do eating disorders have serious physical health consequences, but also their precursors, weight concerns, are associated with obesity and can lead young people to adopt unhealthy weight control behaviors, such as smoking. Thus eating disorders and their precursors are associated with two serious public health problems among young people in the United States. Due to the paucity of prospective cohort studies, little is known about the etiology and course of development of eating disorders in young women and much less is known in men. This study will have sufficient power to detect associations of at least moderate magnitude (e.g., RR> 1.7). By following the approximately 16,000 adolescents in the Growing Up Today Study for five additional years we will have the largest prospective cohort study capturing the time periods of highest risk of developing disordered eating. The size of the cohort and the length of follow-up (9 years) will enable us to answer many questions about the development and course of purging and eating disorders that no other prospective study has the statistical power to address. Moreover, since this is the only large prospective cohort study to assess the development of eating disorders in males, our results will make a lasting contribution to the field.